Mayer, who was in the crowd with Perry, took over his gal pal’s Twitter feed, posting, “John here. Katy can’t write because she’s getting over Stevie Nicks dedicating ‘Landslide’ to us . . . Unforgettable. While I’m at it I have a couple things I’d like to get off my . . . oh, she’s motioning for the phone back. Gotta go!” Perry also attended the opening of Britney Spears’ residency.